[Determination of N'methylnicotinamide and nicotine coenzymes in biological in biological media by the fluorescent method].

Assay of N1-MNA was conducted in 96 urine samples using two methodological variants with external and internal N1-MNA standards. Basing on significant fluctuations of the percent of detecting N1-MNA added to urine, the necessity of using the internal standard was proved. A significant (up to 30%) overestimating of the values in using the external standard makes difficult revealing niacin deficiency. It has been recommended that NAD preparation be used as an internal standard in NAD + NADP assay in the blood, that permits one to simplify significantly the counting and to avoid the universal coefficient (used in literature) of recalculating N1-MNA fluorescence to nicotinamide coenzyme fluorescence because this coefficient is not a constant value.